It is known that the 1-cyclopropyl-7-substituted-6-fluoro-4-oxo-1,4-dihydro-quinoline-3-carboxy lic acid derivatives of the Formula (I) ##STR5## wherein R stands for a piperazinyl, 4-methyl-piperazinyl or 4-ethyl-piperazinyl group possess high antibacterial activity (Eur. J. Clin. Microbiol. 1983, 2, page 111; J. Clin. Pharmacol. 1985, 25, page 82; Drugs Exptl. Clin. Res. 1985, 5, page 317).
The quinoline carboxylic acids of the Formula I can be prepared by reacting 1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid and a cyclic amine in the presence of a solvent at a temperature of 135.degree.-140.degree. C. for 2 hours (German open application 3,033,157; German open application 3,142,854.